Fundamental research using tissue culture and transplanted tumors in small animals has produced data which indicate that the use of fast neutrons may improve the control rates in cancer patients presently treated with conventional forms of radiations. Clinical neutron programs are presently in progress in Houston, Seattle and the District of Columbia supported by funds from the National Cancer Institute. Several other medical centers plan to join this national effort. A major clinical trial in London sponsored by the British Medical Research Council is underway and published data from the British program indicate that the benefits anticipated of neutron beams may be clinically realized. This application is an extension of a program initiated by the Middle Atlantic Neutron Therapy Association to begin cooperative controlled clinical trials to determine whether fast neutrons can significantly improve current control rates. Present funds for development of this effort are from USPHS/NCI grant 7-P01-CA-17465-02 and interagency agreement #14-01-CO-40001 -modification number 3.